I think the heatsink plate with proper gasket would work amazing in water… so much surface
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This should have been the first comment and the thread could have been closed.
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Yes, way more resistance, but not considering what’s connected to the Focbox, if it states 60A continuous it should handle 60A continuous and not going nuclear after only 40A for 30 seconds IMO ?
I first mounted the Focbox to a big 2mm aluminium plate on the bottom of the board, in direct contact with water. This plate is 300x200m so it should dissipate a lot of heat. The alu plate of the Vesc was mounted to this big plate via thermal grease (Artic MX2 5W/mK) but it didn’t stop the mosfet from hitting 80°C super quickly.
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Hi @somaht21 just a thought for when your designing your solution.
The thermal conductivity of a high-grade thermal paste is 8.5 W/mK, or Thermal pads some 14W/mK .
The heat conductivity of copper is 385 W/mK, or for aluminum 205 W/mK.
So the thermal compound is actually a poor heat conductor when compared to the aluminum itself.
In computers the role of the thermal compound is to fill the tiny gaps between the cooler and the IHS (Integrated Heat Spreader) promoting thermal conductivity (or just to make some additional heat conductivity possible if the two surfaces are convex or concave). In theory maybe the same holds true for your application solution?
Some enthusiasts use lapping between CPU and IHS a process in which two surfaces are rubbed together with an abrasive between them thus smoothing the surfaces giving better contact or heat transference.
Good luck with your solution.
Welcome to esk8 continues power ratings 
Try flipsky 4.20 with 100A or v6.6 with 200A continues ratings 
Some FOCBOX had a plastic between the thermal pad and the mosfet’s that should have been removed at the factory
Make sure yours don’t have it
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These values (100A & 200A) are for Dual setups right ? It indicates “only” 60A continuous for single ESC 6.6, which is what Enertion has rated his focboxes =(
I’ve checked it already but nothing on the silicon.
@Mars, Thanks for the info, really intersting. But as you said, unless you have 2 perfect surfaces in contact, you’ll need thermal grease or thermal pad right ? In this case, I’m only using thermal pad for the contact between FETs and Focbox heatsink and Focbox and Alu- plate. Let’s see what the next trial shows. I’ll let you guys know.
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For the dual it’s 100a per single stated on there website
strange sentence 
But I think you understood
You could use the thinnest thermal pad you manage to find and make a copper or aluminum spacer, this should improve conduction a lot
Just make sure to avoid electrical contact
That’s weird, Single 60A but one side on a Dual 100A… I wouldn’t trust the 100A then!
Yes as I understand it you still need to use a thermal compound. I haven’t used thermal pads. The paste is applied in very thin layers to fill the tiny gaps between the cooler and the IHS or just to make some additional heat conductivity possible if the two surfaces are convex or concave.
So the smoother the surfaces are to start with the better the result.
As @Pedrodemio suggests the thinnest thermal pad a copper or aluminum spacer, avoid electrical contact lol
So basicly we haven’t moved from vesc 4.12. we need higher voltage Esc’s (I know your working one one)
Mosfet case itself is a pin, you need isolating thermal pad or etc stuff
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If you look at the middle of this ride you can see a 27sec Hill climb where mosfet temps get up to 62c. Battery amps between 35-45a. This is with the focbox cooling case. So I guess the definition of continuous has to be defined.
I literally just add aluminum mass… Evo has no external cooling and an extra 1/4" thick piece of aluminum big enough to rest two Focbox on top off and screw them to the plate. The only cooling issues I run into are with the motor.
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Really interesting datas. It’s pretty much the same for my focbox. When ppulling 35Amps, the temp doesn’t increase that much but passing 50A it just starts going crazy. I guess 60A continuous is in the best case scenario with a fan blowing cool air on the heatsink. I’ll try the new thermal pad soon but if it doesn’t work out --> Vesc6 !
I thought around 45a was the focbox ceiling? I know DeckyBro has been running high voltage low amps…
Above 45a you run into temp. prob.
So your observation of >50a overheating sounds right 
as for v4.12 I thought that was max 28-30a
How many Amps are you running @Deckoz?
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On Enertion’s website it’s written “60A continuous - 120A Burst”. For me, “continuous” means that you could have it run for 10 minutes without reaching the FETs temp limit (so around 80-90°C). From my experience and what I’ve read, it’s just not true.
No it is not.
& to be honest pushing a prop through water is like trying to ride through quicksand! So likely you will need to be conservative as compared to a eSk8.
Even with a VESC 6… I’m not sure if you could load it with 80a for 10 minutes without thermal cut-off just because I have not seen anyone do that in the real world, only static tests by Vedder. And then his design has been shown to be limited by thermal transfer hence the proliferation of heatsinks for all designs. No doubt v6 is a big step up from v4 but it still has limitations.
So many variables from battery to loom to speed controller to loom to motor… and everything else in-between.
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